Contact lenses often have complex geometries to accomplish intended optical outcomes. By way of example only, corneal refractive therapy contact lenses are used to treat a variety of visual acuity deficiencies. These lenses provide treatment by altering the shape of a patient's cornea, which adjusts the focal point of light within the eye and causes it to properly focus on the retina to enhance vision.
Corneal refractive therapy lenses are commonly described in terms of a plurality of zones, such as a central zone, a connecting zone and a peripheral zone. Generally speaking, the central zone fits onto the cornea of a patient and exerts a specific amount of pressure to flatten the cornea. The connecting zone allows adequate room for tearing and displacement of the cornea during treatment, and the peripheral zone grips the surface of the eye. That said, each zone may be shaped differently to accomplish its function.
For example, FIG. 1 illustrates a conventional corneal refractive therapy lens 100, which includes central zone 110, connecting zone 120, and peripheral zone 130. Central zone 110 is generally spherical and has a first radius of curvature, connecting zone 120 has a second radius of curvature that is generally steeper (shorter radius) than the radius of curvature of the first zone, and peripheral zone 130 has a third radius of curvature that is generally flatter (larger radius) than the radii of curvature of the central and connecting zones. Although the zones are illustrated as substantially spherical in FIG. 1, depending upon the patient's pathology, the zones may be any shape suitable to effect treatment, such as aspherical or sigmoidal, or may be combination of spherical, aspherical and/or sigmoidal shapes.
Corneal refractive therapy contact lenses are commonly machined or molded from a single, continuous piece of polymer material. As such, given the above-described complex shape of corneal refractive therapy lenses, a disadvantage of these lenses is that it can be difficult for lens fitters to communicate the precise shape of the lens to the manufacturer.
Conventional systems and methods of communicating the shape of the lens require the lens fitter to designate points of origin of the radii of curvature along the central axis of the lens. However, the radii of curvature of the connecting and peripheral zones may be different than the radius of curvature of the central zone. As such, restricting the location of the point of origins to the central axis limits the lens fitter's choice of shape for these zones.
For example, FIG. 2 illustrates contact lens 200 comprising central zone 210 and connecting zone 220. As shown, the point of origin of the radius of curvature of central zone 210 is shown as point 212 on central axis 214. However, the point of origin of connecting zone 220 is point 216 on axis 217. Selection of a point of origin on central axis 214, such as point 218, would result in a differently-shaped connecting zone, possibly causing discomfort to the wearer and reduced efficacy.
That said, a disadvantage of such conventional systems is that it is difficult to ascertain and communicate the location of points of origin lying off the central axis (such as in the connecting and peripheral zones) without complex geometric computation.
Accordingly, it would be advantageous to provide a method for defining and communicating the shape of the contact lens (whether or not intended for corneal reshaping) to the manufacturer that does not require the lens fitter to specify points of origin for the radii of curvature.